Rotary kiln lining



Jan. 28, 1941. R. P. HEUER 2,230,141

ROTARY KILN LINING Filed Oct. 24, 1939 IIIIIII/I/III/I/ Patented Jan.28, 1941 UNITED STATES PATENT OFFICE General Refractories ofPennsylvania Compa LV, a corporation Application October 24, 1939,Serial No. 300,999

I 7 Claims.

The present invention relates to refractory linings for rotary kilns.

A purpose of the invention is to restrict heat losses from a rotary kilnwithout shortening the 6 life of the refractory lining or rendering thelining more susceptible to failure through crushing.

A further purpose is to provide insulating means for a refractory liningwhile providing a unitary column support for he individual bricks of thelining directly on the metallic shell of the kiln.

A further purpose is to prevent the possibility of lateral change ofrelation between refractory lining elements and insulating elements ofro- 16 tary kilns.

A further purpose is to employ nonacid refractory lining bricks,preferably unburned, in a rotary kiln, to integrate-the bricks to oneanother by oxidizable metallic spacer plates and to prevent destructionof the integrated joint by providing unitary column support of eachbrick on the metallic shell of the kiln.

A further purpose is to provide magnesite or other nonacid refractorybricks in a rotary kiln with an adequate base and 'a base which isunshiftable as far back as the metallic shell of the kiln.

Further purposes appear in the specification and in the claims.

80 In the drawing no attempt has been made to illustrate all of thepossible forms in which the invention may be embodied. The forms shownin the drawing have been chosen from the standpoint of satisfactoryoperation and convenient 36 illustration of the principles involved.

Figure 1 is a transverse section through a rotary kiln, the section notbeing quite vertical because the kiln is sloping with respect to thehorizontal. Figure 1 is diagrammatic as to de- 40 tails not important tothe invention.

Figure 2 is an enlarged fragment of Figure 1.

Figure 3 is a perspective view of. one of the bricks of Figures 1 and 2.

Figure 4 is a section of Figure 3 on the line Figures 5, 6, '7 and 8 areperspective views of variations in the character of the bricks, Figur 7being to reduced scale. 4

Figure 9 is an end elevation of a variant form 60 of brick.

In the drawing like numerals refer to like parts.

The following description is by way of illus- (crass-a2) rotary cementkiln, but also to include the rotary calcining kiln used in thepreparation of ores, building materials, refractory materials and thelike.

In the comparatively recent past, rotarykilns 5 were provided with arefractory lining of fire, clay or high alumina brick which was notinsulated in the burning zone. The problem of insulation in the burningzone, using brick of the character mentioned, was not solved because [0the insulation increased the temperature of the working face of suchbrick beyond the point which the brick could stand when in contact withlime and other fluxes present in the charge. In the zone of intermediatetemperature, between 15 the burning zone and the preheating zone, therefractory brick were frequently surrounded by a separate annular layerof insulating brick which rested against the outershell or supportingstructure of the kiln.

More recently success was had in employing nonacid refractory brick,particularly magnesite (magnesia) brick, in the burning zone. This zonewas then insulated by inserting between the nona'cid refractory bricklining and the kiln shell, a 25 separate course of insulating bricks ofperhaps 1 inch to 2% inches in thickness.

This arrangement of an inner refractory lining and a separate heatinsulating brick layer has caused difliculty through short life of thelining. Study of the problem by the present inventor indicates that amajor factor in such reduced lining life is slight lateral shift betweenthe inner annulus or layer of refractory brick and the outwardlyadjoining annulus or layer of heat insulating brick. In many cases theheat insulating brick do not conform exactly to the dimensions of theouter surfaces of the refractory brick, even when the lining isoriginally installed, so that an individual refractory brick may bebacked up in part by one insulating brick and in part by another, oreven conceivably in part by four different insulating bricks. Even ifthis condition does not occur when the lining is installed, shifting ofthe inner annulus or layer of refractorybricks with 48' insulatingmaterial.

preciated when we remember'that, during each rotation of the kiln, eachrefractory brick shifts from a condition of no load (topmost position),to a condition of maximum load when it is under maximum compression fromthe weight of the charge and the weight of the linin (lowermostposition). When the inner layer or refractory bricks shifts with respectto the outer layer of heat insulating bricks; the chance that anindividual refractory brick will be unevenly based on parts of severalinsulating bricks, or will shift its base from one heat insulating brickto another with consequent change in its loading, is relatively great.Under these conditions the possibility of localized uneven loading ofthe heat insulating bricks is considerable and heat insulating bricksundergo crushing. Once a heat insulating brick begins to give way,localized loading on adjoining bricks is increased and progressivefailure of the base of the refractory bricks occurs with development ofconcentrated stress in the refractory bricks, and failure of therefractory bricks themselves.

The present inventor has discovered that, without loss of the advantageof a heat insulated lining, an individual column support, firm andunshiftable, may be carried back to themetallic shell for eachindividual refractory brick. Thus each individual refractory brickretains the same basethroughout the life of the lining, and thepossibility of shifting its base or being based partly on one heatinsulating brick and partly on another is entirely prevented.

This result is preferably accomplished by using a unitary brick whoseworking face is of nonacid refractory material and whose cold face is ofheat Under this arrangement, no matter how much the brick as a whole maychange its position, it is always assured of an integrally united eveninsulating base.

The principles of the present invention are particularly desirable in alining whose bricks are integrated together by oxidizable metallic"spacer plates. The integrally united insulating base of the presentinvention prevents uneven stressing of the refractory bricks and thuspref vents breaking of the joint between bricks p r duced by theoxidizable metallic spacer plate. Thus in rotary kilns the integrationof bricks'by means of oxidizable metallic spacer plates is very muchmore permanent where the refractory bricks are integrally based on themetallic shell, than where a separate insulating layer is employed.Oxidizable metallic spacer plates are' particularly desirable whereunburned nonacid brick .are being used, since'unburned nonacid brick,

particularly magnesite brick, shrink to a considerable extent duringuse, and growth of the spacer plates with oxidation, due to the factthat the oxide occupies a larger space than the original metal,compensates for the shrinkage of the refractory bricks and preventslooseness of the joints due to shrinkage.

Figure 1 illustrates a typical rotary kiln such as a cement kiln orcalcining kiln for ores, building materials, refractories or the like.The outer supporting structure of the kiln consists of a metallic shell29 having at intervals metallic bands 2! which turn on rollers 22rotatably supported on permanent structure, not shown. The mechanism forrotating the kiln is not important to the present invention and is notillustrated. Within the metallic shell 29 is a refractory lining 23consisting of refractory bricks 24, as

shown more in detail in Figures 2, 3 and 4. Each of the briks 24 has ahot face 25 and a cold face 26, wh ch is usually referred to herein asthe base. It is important to note that the cold face 26 rests directlyupon the metallic shell 20, so that there is direct and nonshiftablecolumn support by an integral brick extending clear through from the hotface 25 to the cold face or base 26.

The brick 24 consists of two portions, 9. refractory portion 21 and aheat insulating portion 28 united at 29 preferably by refractory cement.A suitable refractory. cement is a clay base cement containing sodiumsilicate. Or the cement of Heuer U. S. Patent No. 1,714,506, granted May28, 1929, for Brick and cement for furnace use may be employed ifdesired.

The refractory portion 21 of the brick will preferably be nonacidrefractory such as magnesite (magnesia), chrome (chrome-iron ore),chrome-magnesite or magnesite-chrom'e. Most desirably the refractorywill be unfired, that is,

facture; No. 1,851,181, granted March 29, 1932,

for Dense mix for refractories and process of preparing the same} No.1,859,512, granted May 24, 1932,'for Refractory and method of making it;No, 1;992,482, g'rantedFeb. 26, 1935, for Highpressure brick containingmagnesia, and procvess of making thasame; No. 1,992,483, grant Feb. 26,1935, for High pressure chrome refractory; No. 2,068,411, granted Jan.19, 1937, for Highpres'sure -non'plastic refractory and method of makingthe same; No. 2,087,107, granted July 13, 1937,-for Chrome-magnesiarefractory and method; No. 2,154,813, granted April 18, 1939, .forSuspended furnace roof; and No. 2,155,165, granted April 18, 1939, forFurnace roof. These patents are incorporated herewith by reference andmade a part hereof.

The heat insulating portion 28 of. the brick may desirably be made ofasbestos, diatomaceous earth, or more refractory materials such askaolin or fire clay provided with high pore space, as due to burning outof organic matter or evolution of gas, as well known in the art ofpreparing heat insulating materials. The insulating material willpreferably have a cold crushing strength greater than 250 pounds persquare inch.

Ordinarily it will be preferable to mold the portions 21 and 28separately and to secure them together with suitable furnace cement asJust described. It will however be permissible to mold one or the otherportion first, and then unite the other portion to it by placing theportion first? molded in a mold and molding the later-formed portion incontact with the portion thus uniting the two together.

It is very desirable in many installations to integrate the refractorytogether by the integrating action of oxidizable metallic spacerplates,.

suitably plates of sheet iron or steel of suitable thickness, such as A34 or inch in thickness. Spacer plates are shown at 30 covering one ofthe longitudinal faces 3| of each brick. The spacer plates willordinarily be applied in their first formed,

unoxidized or as rolled condition, and as the kiln is heated they willbecome oxidized and will unite to the nonacid refractory material oneach side as explained in Heuer Uf. S. Patents Nos. 2,154,813 and2,155,165, above referred to. I

The plates may be loose or fastened to the bricks prior to installation,and any suitable means of fastening of the plates to the bricks may beemployed. Figures 1 to 5 illustrate plates fastened to the bricks byco-moldlng, that is, placing the formed plate in the mold at the timethe brick is molded. During the molding, projectingfingers 32 from sidearms 33 of the plates are suitably embedded in the bricks to interlockthe plates with the bricks. Co-molding of spacer plates and bricks isshown in Heuer U. S. patent application Serial No. 198,426, filed March28, 1938, for Refractory brick process, machine and structure; and inSerial No. 238,505, filed November 3, 1938, for Refractory brickstructure.

Metallic spacer plates may be affixed to the brick in any'other suitablemanner, as by cementing to the faces of the brick, shown at 34 in Figure6, or resiliently gripping the brick by the spacer plate as shown inFigure 7, where the side arms 33' of the spacer plate resiliently gripthe brick, preferably fitting into a slight recess 35 molded onthe faceof the brick. In the form of Figure 7 the spacer plate may convenientlybe aflixed at or immediately before the time of installation of thebrick.

It ordinarily is not economical to extend the spacer plate to cover theinsulating portion 28 of the brick, as the chemical reaction with thespacer plate which integrates the bricks does not take place with theinsulating material ordinarily used. Therefore in Figures 1 to 5, thespacer plate 30 extends only over the longitudinal face of the nonacidrefractory.

Where very high temperatures are used, it may be necessary to keep therear end of the spacer plate in contact with the metallic shell tosufficiently cool the spacer plate by conduction of heat and prevent theunoxidized rear portion from melting out. For this purpose the spacerplate may extend over the entire side of the brick as shown at 30' inFigure 6.

In some instances it is desirable to extend the spacer plate over therefractory and the heat insulation on one of the side faces of thebrick, and also over the cold face. In this case the plate assists inmaintaining the bond at 29 between the refractory and the heatinsulation, armors the corners of the relatively weak heat insulation atthe cold face, and insures good heat transfer contact between the spacerplate and the metallic shell. Figure 9 illustrates a brick having anintegral oxidizable metallic spacer plate 30 of L form covering thelongitudinal face 3| of the brick and the cold face 26. The spacer plate30 is desirably cemented to the brick.

It is usually desirable to employ the spacer plate only on thelongitudinal faces of the bricks, but if preferred, the spacer plate mayextend over a longitudinal and an end face also as shown at 36 in Figure6. In order that the spacer plates may contact refractory on both faces,avoiding as much as possible contacting of a spacer plate on one brickwith a spacer plate on an adjoining brick (except at the small armportions 33), it is preferable to place the spacer plate only on onelongitudinal face, and if desired, also on one lateral face of thebrick.

While spacer plates are desirable, the invention may be applied withoutusing spacer plates. Figure 8 illustrates a brick 24' which is like thebricks of Figures 1 to 5 except that it has no spacer plate attached toit. This brick can be laid with mortar or with a loose spacer plate asdesired.

The thickness of the refractory lining and'the relative proportion ofthe lining which consists of the refractory material 21 and theinsulating material 28 will of course depend upon the design of thefurnace and particularly the working temperature. In order to illustratethat the insulating material may in an individual case be a smaller -orlarger proportion of the total thickness of the lining, Figure 5illustrates a brick in which the insulating material 28 is relativelythinner than that in Figure 3.

The relative dimensions of the brick are of course not critical in thepresent invention. Whereas Figures 1 to 6 illustrate brick of wedgeshape, with the longer cross-sectional dimension lengthwise of thefurnace, key brick may be employed, with the longer cross-sectionaldimension extending annularly and the spacer plate on one of the taperedfaces, as shown at 24' in Figure '7.

It will be evident that in each of the forms of the invention, the meansfor insulating at the cold face and the refractory at the hot face areintegrally united and function as a single unitary column, providing anadequate base and an unshiftable base for the refractory, and carryingback the load clear through to the cold face of the insulating means, atwhich point it is applied to the outside metallic shell of the rotarykiln.

In view of my invention and disclosure variations and modifications tomeet individual whim or particular need will doubtless become evident toothers skilled in the art, to obtain all or part of the benefits of myinvention without copying the structure shown, and I, therefore, claimall such in so far as they fallwithin the reasonable spirit and scope ofmy invention.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A rotary kiln having a metallic shell, in combination with a kilnlining consisting of unitary bricks extending clear through from theinterior of the lining to the metallic shell and providing direct andunshiftable column support for the hot face from the shell, the interiorof each individual brick consisting of nonacid refractory in unfiredcondition, and the exterior consisting of heat insulating material andthe exterior and interior portions being integrally and unshiftablyunited.

2. A rotary kiln having a. metallic shell, in combination with arefractory lining consisting of unitary bricks extending from the shellto the hot face, there being unfired nonacid refractory material at theportions of the bricks toward the interior of the kiln and heatinsulating material extending over the entire face of the brickadjoining the metallic shell, the refractory and heat insulatingmaterial being integrally and unshiftably united, and oxidiza'blemetallic spacer plates interposed between unfired nonacid refractorymaterial of adjoining bricks.

3. A rotary kiln lining consisting of unitary bricks extending from thehot face to the metallic structural support of the lining, said bricksconsisting of nonacid refractory material at the hot face and heatinsulating material extending over the entire cold face,-the refractoryand heat insulating materials being integrally and unshiftably unitedand the heat insulating material providing an individual base for therefractory material of each brick, unshlftable with respect to therefractory material of that brick, and oxidizable metallic spacer platesbetween nonacid refractory material of adjoining bricks.

4. A rotary kiln brick having a hot face and a cold face, the portion ofthe brick adjoining the hot face consisting of nonacid refractory material, the portion of the brick adjoining the cold face consisting ofheat insulation and the two being integrally and unshiftably unitedtogether.

5. A rotary kiln brick having a hot face and a a cold face, the portionof the brick adjoining the hot face consisting of nonacid refractorymaterial, the portion of the brick adjoining the cold face consisting ofheat insulating material,

, and the two being integrally united together and an oxidizablemetallic spacer plate secured to one of the faces of the brick coveringthe nonacid refractory material at that point.

6. A rotary kiln brick having a hot face and diza'ble-metallic spacerplate secured to one of the faces of the brick covering the nonacidrefractory material and the heat insulating material of that face,whereby the unoxidized portion of the spacer plate may be cooled duringuse by contact with external metallic structure.

7. The rotary kiln 'brick having a hot face, a cold face and. a sideface, the material of the brick adjacent the hot face consisting ofrefractory and the material adjacent the cold face consisting of heatinsulation, the refractory and the heat insulation being integrally andunshiftably united, and an oxidizable metallic spacer plate extendingover the side face and the cold face.

RUSSELL P. HEUER.

